Anecdotally, I see few people replacing their apple device (for an other one) because of battery life, and conversely stories of apple stores replacing batteries/devices because of battery life issues are regular.
All in all, I don't think they'd care. Their biggest business these days is phone & tablet, and battery life (and the failure thereof) is not the primary upgrade driver.
Battery life was one of the big things that OS X 10.9 touted as an improvement. Apple expended significant engineering effort in reducing energy use to squeeze more out of their current batteries[1]. On the mobile side of things, they developed the M7 co-processor to allow access to sensor data without having to wake up the CPU, and famously never supported flash, both in an apparent attempt to save battery life. They seem to me to be very interested in battery life and I think any technology that could increase it by significant margins would be something they would snap up.
All in all, I don't think they'd care. Their biggest business these days is phone & tablet, and battery life (and the failure thereof) is not the primary upgrade driver.